(37) L is too big when compared with actual observations. Therefore 

 the average "wave length" cannot be computed from the observed 

 distribution of the "periods". The individual "wave lengths" computed 

 from the individual "periods" have therefore a very doubtful meaning. 



With reference to "wave lengths", the only reliable formula is for 

 the average "wave length" for a fully developed sea as given by 

 equation (37). For swell, the average "wave length" is approximately 

 given by the classical formula using the average "period" of the swell. 

 For seas not fully developed or for cross seas, no convenient formulas, 

 in general, exist. 



However, for newly generated partially developed seas in which B. 

 is less than 0.5, it is _possible to obtain an approximate value for L,. 

 Under these conditions, H, is given by 



L, = 2.56 T.^ (50) 



1 



The method for deriving equation (50) involves short-crested seas 

 and employs approximations and procedures similar to those used 

 in equations (33) through (36). 



E. Wave "Speeds" 



1. Theory - A Contradiction 



The usual wave observation procedure has been that of observing 

 the "periods" of the waves and computing the average "period". The 

 "wave lengths" and "speeds" of the individual waves are rarely 

 independently observed. 



The theories given above suggest that the average "wave length" 

 of a fully developed sea is two- thirds of the value given by the classical 

 formula. Also some independent observations suggest that these 

 theories are more nearly correct. 



In c.g.s. units, the two classical formulas for the speed of a wave 

 crest are given by 



C = L/T (51) 



and 



C = gT/2ir . (52) 



In terms of average "periods" and average "wave lengths" in 



43 



